Reduced divergence electromagnetic field configuration

ABSTRACT

A photon beam dose enhancement is controlled by configuring at least two magnets in a staggered opposing coil configuration, such that the first central field vector of the first magnet is more anti-parallel than parallel to the second central field vector of the second magnet. In one form, the first central field vector of the first magnet is rotated between ±90° to 180° to the second central field vector of the second magnet. Typically, the first central field vector is noncoaxial with the second central field vector. The resulting magnetic field configuration has a larger portion of higher magnitude magnetic field that can reach deeper into a target body and provides additional space within the region of higher magnitude that can accommodate larger portions of a body.

This application claims benefit of U.S. provisional application60/472,080 filed 20 May 2003.

The electromagnetic field comprises at least a first magnetic field,which is opposed by at least a second magnetic field.

The first magnetic field has a first central field vector and the secondmagnetic field has a second central field vector. The first centralfield vector is more anti-parallel than parallel to the second centralfield vector. In one form, the first central field vector is staggered,or non-coaxial, with the second central field vector.

In one form, the first central field vector is displaced orthogonallyfrom the second central field vector so that at least a portion of acombined field diverges less rapidly than the first magnetic fieldalone. The first central field vector can be displaced by two orthogonalcomponents.

The first magnetic field can be produced by any means which can producemagnetic fields such as permanent magnets, current carrying coils,combinations of current carrying coils, and combinations of these.

The second magnetic field can be produced by any means which can producemagnetic fields such as permanent magnets, current carrying coils,combinations of current carrying coils, and combinations of these.

Magnetic field gradients can be used to enhance the cancer therapycapabilities of high-energy photon beams as taught in U.S. Pat. No.5,974,112, which is incorporated herein by reference. For cancertherapy, as well as for other situations, it is very desirable to havemore ready access to a region of comparatively high field and/or highfield gradients than is typically available on the interior of asolenoid or in the gap between a so-called split aiding pair. (Such asplit pair is comprised of two coaxial solenoids arranged along a commonaxis with a space between them and with the currents in both members ofthe pair circulating in the same direction.)

Here is disclosed a novel magnet pair configuration better-suited toprojecting magnetic fields and gradients into objects too large to fitinto the interior of a solenoid or into the gap in a split pair. Thenovel arrangement is termed a Staggered Opposing Coil Configuration(SOCC) and is shown in the accompanying figures.

In practicing the teachings of U.S. Pat. No. 5,974,122 using magnets inthe SOCC configuration disclosed hering, for example, the tumor ortarget region in the patients body may be in the step in the magnetsystem as depicted in FIGS. 5-7 and 9-11.

FIG. 1 is a section of a magnet with the field lines depicted.

FIG. 2 is a section of two magnets in a Staggered Opposing CoilConfiguration with field lines depicted, where the first central fieldvector of the first magnet is anti-parallel to the second central fieldvector of the second magnet.

FIG. 3 is a section of two magnets in a Staggered Opposing CoilConfiguration with field lines depicted, where the first central fieldvector of the first magnet is orthogonal to the second central fieldvector of the second magnet.

FIG. 4 is a section of two magnets in a Staggered Opposing CoilConfiguration with field lines depicted, where the first central fieldvector of the first magnet is rotated between ±90° to 180° to the secondcentral field vector of the second magnet.

FIG. 5 shows elements of a photon beam radiation system, with magnets(in cross-section) having anti-parallel central field vectors, tocontrol dose enhancement.

FIG. 6 shows elements of a photon beam radiation system, with magnets(in cross-section) having orthogonal central field vectors, to controldose enhancement.

FIG. 7 shows elements of a photon beam radiation system, with magnets(in cross-section) having central field vectors with an axial offsetbetween ±90° to 180° with respect to another central field vector, tocontrol dose enhancement.

FIG. 8 is a perspective view of the magnets in the configuration of FIG.6.

FIG. 9 shows elements of a photon beam radiation system, with magnets(in cross-section) in an anti-parallel configuration, to control doseenhancement to a torso target area

FIG. 10 shows elements of a photon beam radiation system, with magnets(offset between=90° to 180° with respect to one another) in ananti-parallel configuration, to control dose enhancement to a torsotarget area.

FIG. 11 shows elements of a photon beam radiation system, with magnets(offset between ±90° to 180° with respect to one another) in ananti-parallel configuration, to control dose enhancement to a prostratetarget area

Referring to FIG. 1, a coil magnet 10 (shown in section) generates amagnetic field 20 having a central field vector 15. The color of themagnetic field lines indicates the magnitude of the field, such thatareas of highest to lowest field and/or field gradients are red 21(highest), followed by orange or yellow 22, green 23 and blue 24(lowest).

Referring to FIG. 2, two coil magnets 30 a, 30 b (shown in section) arein a Staggered Opposing Coil Configuration, each magnet 30 a, 30 bcontributing to an overall magnetic field 40. The first central fieldvector 35 a of the first magnet 30 a is rotated is anti-parallel to(rotated 180° from) the second central field vector 35 b of the secondmagnet 30 b. The color of the magnetic field lines indicates themagnitude of the field, such that areas of highest to lowest fieldand/or field gradients are red 41 (highest), followed by orange oryellow 42, green 43 and blue 44 (lowest). Comparing the magnetic fieldsbetween FIGS. 1 and 2 shows a larger portion of higher magnitudemagnetic fields especially along the interior lines 46 between magnets30 a and 30 b in FIG. 2.

Referring to FIG. 3, two coil magnets 50 a, 50 b (shown in section) arein a Staggered Opposing Coil Configuration, each magnet 50 a, 50 bcontributing to an overall magnetic field 60. The first central fieldvector 55 a of the first magnet 50 a is rotated is orthogonal to(rotated 90° from) the second central field vector 55 b of the secondmagnet 50 b. The color of the magnetic field lines indicates themagnitude of the field, such that areas of highest to lowest fieldand/or field gradients are red 61 (highest), followed by orange oryellow 62, green 63 and blue 64 (lowest). Comparing the magnetic fieldsbetween FIGS. 1 and 3 shows a larger portion of higher magnitudemagnetic fields especially along the interior lines 66 between magnets50 a and 50 b in FIG. 3.

Referring to FIG. 4, two coil magnets 70 a, 70 b (shown in section) arein a Staggered Opposing Coil Configuration, each magnet 70 a, 70 bcontributing to an overall magnetic field 80. The first central fieldvector 75 a of the first magnet 70 a is rotated between ±90° to 180° tothe second central field vector 75 b of the second magnet 70 b. In thiscase, the first central field vector 75 a is rotated approximately −135°(+225°) to the second central field vector 75 b. The color of themagnetic field lines indicates the magnitude of the field, such thatareas of highest to lowest field and/or field gradients are red 81(highest), followed by orange or yellow 82, green 83 and blue 84(lowest). Comparing the magnetic fields between FIGS. 1 and 4 shows alarger portion of higher magnitude magnetic fields especially along theinterior lines 86 between magnets 70 a and 70 b in FIG. 4.

In FIGS. 1-4, it can be seen that the fields generated by the opposingcurrent directions in the coils efficiently add together only in alocalized region where the windings of the two coils most closelyapproach each other. This tends to project the desired field vectorsfurther into the target region while not generating extremely large anddifficult-to-control magnetic forces between the SOCC components. Inother words, the magnetic field that results from using two magnetshaving central field vectors that are offset by ±90° to 180° from oneanother has a larger portion of a comparatively higher magnitude ofstrength of the magnetic field and/or higher gradient compared to themagnetic field from a single magnet. This results in a gain of 1, 2, 3or more centimeters in depth for higher magnitudes of magnetic fieldswhich can be especially useful for targeting tumors in a body with aphoton beam source. It should be noted that the first central fieldvector is typically staggered, or non-coaxial, with the second centralfield vector.

Referring to FIGS. 5-7, there is shown a radiation system having aphoton beam source 121 which produces an incident photon beam along abeam path, the beam path being defined by all of the paths of theincident photons in the beam. Though this beam path, can have acomplicated cross section, a beam vector 101 can be chosen to representthe beam path. The photon beam is indicated by the point 122 on the beamvector 101. The beam vector 101 enters a body 123 at the point 124 andthe incident photons generate an electron-photon cascade along the beampath, the electron-photon cascade being indicated by the point 125 onthe beam vector 101 in the body 123.

At the energies of interest here the path of the electron-photoncascade, being the collection of the paths of the particles in theelectron-photon cascade, can be considered to follow along the incidentphoton beam path. Thus, the electron-photon cascade can also berepresented by the beam vector 101, so that beam path here means boththe incident photon beam path and the beam path of the electron-photoncascade. The radiation system has a photon beam source which provides aphoton beam incident on a body along a beam path. The photon beamgenerates an electron-photon cascade along the beam path in the body. Adose enhancement control device comprises a pair of magnets in a SOCCconfiguration. The SOCC magnet configuration results in a magnetic fieldconfiguration with a magnetic field component across the beam path andwith a magnetic field gradient component along the beam axis which causea relative dose profile, the relative dose profile being controlled bycontrol of the magnetic field configuration. Further details concerninghow the radiation system can be used, for example, the tumor or targetregion in the patients body may be in the step in the magnet system areshown in U.S. Pat. No. 5,974,122.

As suggested in FIGS. 9-11, SOCC magnet pairs can be made in any sizeand can be applied to many target regions including, but not limited to,those in the human torso, the pubic region, or the prostrate region. Themembers of a SOCC pair need not be of the same size. The magnet axes maybe skewed with respect to each other and need not lie in the same planenor be in the same plane as, for example, a photon beam that might beused for cancer therapy. The photon beam may target the cancer at avariety of angles and directions and need not be used from anyparticular reference point with respect to the SOCC pair. The magnets ofa SOCC can be moved with respect to each other during use or adjustedbetween uses to affect the position and shape of the fields generated.Such changes can be controlled and coordinated with changes of photonbeam characteristics such as when IMRT (Intensity Modulated RadiationTherapy) procedures are used in the treatment of cancer. While simplecoils are shown, a given coil can be an array of coils. While magnetcoils are typically wound as circular solenoids, other cross-sectionalshapes such as racetracks and ovals may be usefully employed.

The SOCC arrangement can be employed using permanent magnets as one ormore of the field sources.

The teaching herein can be applied to manipulating electron beams orbeams of other types of charged particles.

In use, the radiation system uses a dose enhancement method that caninclude choosing a relative dose profile and configuring at least twomagnets in a SOCC configuration so that the resulting magnetic fieldconfiguration has a magnetic field component across the beam path with amagnetic field gradient component along the beam path which cause therelative dose profile, the relative dose profile being controlled bycontrol of the magnetic field configuration. The magnetic fieldconfiguration can be controlled by, among other things, adjusting therelative placement of the magnets with respect to one another. Themagnetic field configuration can also be controlled by moving at leastone of the magnets in the SOCC configuration.

As shown in FIGS. 5-7 and 9-11, a first magnet can be placed adjacentone portion of a body and a second magnet can be placed against secondportion of the body such that the magnets are in a SOCC configuration.In one form, a first magnet is placed in the area of the groin while thesecond magnet is placed in the area of the buttocks in order to treat atumor in the prostrate area or in the groin region. In another form, thefirst magnet is placed adjacent one portion of the torso while thesecond magnet is placed adjacent another portion of the torso to treat atumor within the torso, such as in the lungs. In another form, the firstmagnet is placed adjacent one portion of the head while the secondmagnet is placed adjacent another portion of the head to treat a tumorwithin the head, such as in the brain. In another form, the first magnetis placed adjacent one portion of the neck while the second magnet isplaced adjacent another portion of the neck to treat a tumor within theneck, such as in the lymph nodes.

1. A radiation system, comprising a photon beam source which provides aphoton beam incident on a body along a beam path, the photon beamgenerating an electron-photon cascade along the beam path in the body, adose enhancement control device comprising at least two magnets, a firstmagnet has a first central field vector and a second magnet has a secondcentral field vector with the first central field vector and the secondcentral field vector being offset between ±90° to 180° with respect toone another.
 2. The device of claim 1, wherein the at least two magnetshave a combined magnetic field configuration with a magnetic fieldcomponent across the beam path and with a magnetic field gradientcomponent along the beam axis which cause a relative dose profile, therelative dose profile being controlled by control of the magnetic fieldconfiguration.
 3. The device of claim 1 wherein the first central fieldvector and the second central field vector are non-coaxial.
 4. Thedevice of claim 1 wherein the first magnet is placed adjacent oneportion of the body and the second magnet is placed adjacent anotherportion of the body.
 5. The device of claim 1 wherein the first centralfield vector is orthogonal to the second central field vector.
 6. Themethod of claim 5 wherein the magnetic field configuration is controlledby moving at least one of the at least two magnets.
 7. The method ofclaim 6 wherein the magnetic field configuration is controlled byadjusting the relative placement of at the first magnet with respect tothe second magnet.
 8. In a radiation system, the radiation system havinga photon beam source which provides a photon beam incident on a bodyalong a beam path, the photon beam generating an electron-photon cascadealong the beam path in the body, a dose enhancement control devicecomprising at least two magnets, a first magnet has a first centralfield vector and a second magnet has a second central field vector, thefirst central field vector and the second central field vector arenon-coaxial.
 9. The device of claim 8 wherein the first central fieldvector is more anti-parallel than parallel to the second central fieldvector.
 10. The device of claim 8 wherein the first magnet is placedadjacent one portion of the body and the second magnet is placedadjacent another portion of the body.
 11. The device of claim 9 whereinthe first central field vector is anti-parallel to the second centralfield vector.
 12. A dose enhancement method used in a radiation system,the radiation system having a photon beam source which provides a photonbeam incident on a body along a beam path, the photon beam generating anelectron-photon cascade along the beam path in the body, the doseenhancement method comprising the steps: choosing a relative doseprofile; configuring at least two magnets, a first magnet having a firstcentral field vector and a second magnet having a second central fieldvector, the first central field vector and the second central fieldvector are non-coaxial; and wherein the resulting magnetic field has amagnetic field component across the beam path and with a magnetic fieldgradient component along the beam path which cause the relative doseprofile, the relative dose profile being controlled by control of themagnetic field configuration.
 13. The method of claim 12 wherein themagnetic field configuration is controlled by moving at least one of theat least two magnets.
 14. The method of claim 12 wherein the magneticfield configuration is controlled by adjusting the relative placement ofthe magnets with respect to one another.
 15. The method of claim 12further comprising placing the first magnet adjacent one portion of thebody and placing the second magnet adjacent another portion of the body.16. The method of claim 12 wherein the first central field vector ismore anti-parallel than parallel to the second central field vector. 17.The method of claim 12 wherein the first central field vector and thesecond central field vector being offset between ±90° to 180° withrespect to one another.
 18. The method of claim 17 wherein the firstcentral field vector is orthogonal to the second central field vector.19. The method of claim 17 wherein the first central field vector andthe second central field vector being offset between ±100° to 170° withrespect to one another.
 20. The method of claim 19 wherein the firstcentral field vector and the second central field vector being offsetbetween ±110° to 160° with respect to one another.
 21. The method ofclaim 20 wherein the first central field vector and the second centralfield vector being offset between ±120° to 150° with respect to oneanother.
 22. The method of claim 21 wherein the first central fieldvector and the second central field vector being offset between ±130° to140° with respect to one another.